Windows 7 / Networking

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Deploying a DHCP relay agent

If you opt to create a centralized or hybrid DHCP infrastructure, you will need a DHCP relay agent on every subnet that does not have a DHCP server on it. Many routers are capable of functioning as DHCP relay agents, but in situations where they are not, you can configure a Windows Server 2012 computer to function as a relay agent, using the following procedure.

1. Log on to Windows Server 2012 using an account with Administrative privileges. The Server Manager window opens.
2. Using the Add Roles and Features Wizard, install the Remote Access role, including the Routing role service.
3. Click Open The Getting Started Wizard. The Configure Remote Access Getting Started Wizard opens.
4. Click Deploy VPN Only. The Routing And Remote Access console appears.
5. Right-click the server node and, on the shortcut menu, select Configure And Enable Routing And Remote Access. The Routing and Remote Access Server Setup Wizard appears.
6. Click Next to bypass the Welcome page. The Configuration page opens.
7. Select Custom Configuration and click Next. The Custom Configuration page appears.
8. Select the LAN Routing check box and click Next. The Completing The Routing And Remote Access Server Setup Wizard page opens.
9. Click Finish. A Routing and Remote Access message box appears, prompting you to start the service.
10. Click Start Service.
11. Expand the IPv4 node. Then, right-click the General node and, in the shortcut menu, select New Routing Protocol. The New Routing Protocol dialog box appears.
12. Select DHCP Relay Agent and click OK. A DHCP Relay Agent node appears, subordinate to the IPv4 node.
13. Right-click the DHCP Relay Agent node and, on the shortcut menu, select New Interface. The New Interface For DHCP Relay Agent dialog box appears.
14. Select the interface to the subnet on which you want to install the relay agent and click OK. The DHCP Relay Properties sheet for the interface appears.
15. Leave the Relay DHCP Packets check box selected, and configure the following settings, if needed.
    • Hop-count threshold: Specifies the maximum number of relay agents that DHCP messages can pass through before being discarded. The default value is 4 and the maximum value is 16. This setting prevents DHCP messages from being relayed endlessly around the network.
    • Boot threshold: Specifies the time interval (in seconds) that the relay agent should wait before forwarding each DHCP message it receives. The default value is 4 seconds. This setting enables you to control which DHCP server processes the clients for a particular subnet.
16. Click OK.
17. Right-click the DHCP Relay Agent node and, on the shortcut menu, select Properties. The DHCP Relay Agent Properties sheet appears.
18. Type the IP address of the DHCP server to which you want the agent to relay messages and click Add. Repeat this step to add additional servers, if necessary.
19. Click OK.
20. Close the Routing And Remote Access console.

At this point, the server is configured to relay DHCP messages to the server addresses you specified.